This invention relates generally to compositions and methods for protecting nylon fibers, yarns and finished products such as carpets from staining, discoloration or degradation, and more specifically to the application of a protective composition that is capable of forming a covalent bond with the nylon.
Carpets constructed from continuous filament and spun nylon yarns have been a major factor in the carpet and floor covering industry for many years. Such carpets offer excellent wear and durability properties along with unlimited coloration and styling potential. The open structure of the nylon fibers makes them easy to dye with a wide variety of dyestuffs such as acid and acid-premetalized dyes, disperse dyes and fiber reactive dyes. Acid dyes are most commonly used in the industry and generally bond with the amine ends in the nylon by an ionic mechanism under acid pH conditions.
The excellent properties of nylon has led to its acceptance for other end uses such as rugs, walk-off mats, upholstery and automotive interiors. Indeed, the fiber has come to rival cotton as the most important fiber in the textile industry.
In spite of its excellent properties, nylon has certain deficiencies which has led to broad usage of competitive fibers such as polypropylene and polyester. While nylon is considered by many to be a hydrophobic fiber and has been described as such in industry literature, it actually is penetrated quite easily by aqueous solutions, almost as easily as cotton. This has created problems with the usage of nylon in the carpet and rug industry and has led to the usage of competitive hydrophobic fibers. One such problem is staining when common colored foods and household products are spilled on a nylon carpet. Artificial colors that are used in products like Kool-Aid and spaghetti sauce are anionic in nature, similar to the acid dyes used to dye the nylon. When these anionic spills are absorbed into the fiber, they will react with the dyesites and produce a permanent stain. Another problem is bleach spots when strong oxidizing agents such as chlorine bleach are spilled on the carpet or intentionally applied in an attempt to remove a stain. The color of the carpet will become lighter and may completely disappear where the bleach is absorbed into the nylon fiber.
Because they are more hydrophobic than nylon, polypropylene and polyester are more resistant to anionic stains and bleach, and a number of products have been developed for application to nylon in order to improve its stain and bleach resistance. Such products are known in the trade as stain blockers and bleach protectors. Such products are typically condensates of formaldehyde with phenolsulfonic or naphtholsulfonic acids, sulfonates of dihydroxydiphenyl sulfone or sulfonated aromatic aldehyde condensates. If they are intended to provide bleach protection, they will contain a group that will act as an antioxidant.
The two things that these products all have in common is that they are aromatic and contain one or more sulfonic acid groups. The sulfonic acid groups cause these conventional products to be anionic under acid pH conditions, which gives them the ability to ionically attach to the amine groups in the nylon. It is suspected that other types of weak bonding may also occur between these conventional stain blockers and bleach protectors and the nylon, such as hydrogen bonding, van der Waals forces and dipole attraction. Resistance to stain occurs because occupation of available amine ends (dyesites) by the anionic charged chemicals will electrostatically repel the similarly charged anionic stain colorants and keep them from bonding with the nylon.
These conventional products have been successfully used in the carpet and rug industries. However, they have one primary drawback. Nylon carpets, rugs and mats are designed to last for many years. Some companies guarantee their products for as long as 20 years. Since the type of bonding which occurs between these anionic stainblockers and bleach protectors and nylon is relatively weak, there is a high probability that the bonds of these conventional protective products with nylon will be broken so that the products will lose some or all of their effectiveness over the anticipated useful life of a carpet product. In the case of carpets, this could occur through repeated steam cleanings and wear in high traffic areas. Rugs are periodically washed and/or dry-cleaned. Mats regularly undergo high temperature laundering. It would be desirable, therefore, if a better-performing stainblocker and bleach protector, that will last for the anticipated lifetime of a carpet product, could be developed. In U.S. Pat. No. 5,998,306, Mura describes technology for producing a series of UV absorbers which have stain-blocker properties based on a specific heterocyclic structure. Such products are said to covalently bond with textile materials but they also act as resist agents for anionic dyes. A process for synthesizing a variety of covalently bonded stain resist products is also described in U.S. Pat. No. 5,316,850 of Sargent and Williams. However, the application procedures of this patent require a two step method by which the chemicals are added separately from and on top of the dyestuffs.
It is well known in the textile industry that fiber reactive dyes which bond covalently with fibers afford the best wet-fastness which can be obtained. Fiber reactive dyes have not gained wide acceptance for use on nylon, however, because of the ease of application, variety of colors and familiarity of acid dyes. However, American Hoechst has described a procedure for applying fiber reactive dyes to unmodified nylons at a pH above 2.5. Hixson et.al. in U.S. Pat. Nos. 5,445,653 and 5,972,046 describe methods for applying fiber reactive dyes to cationic and light dyeable nylon fibers at pH of 1.5 or below by space dye, continuous dye and batch dye methods. In a practice of the procedures described in the Hixson patents, the dyes exhaust uniformly on the nylon in spite of the ultra-low pH conditions at which they are applied, and after formation of covalent bonds with the fiber, can withstand further wet processing at 210xc2x0 F. The inventors have discovered that certain aromatic chemicals that function as colorfastness guards or nylon protectors may be modified to allow them to form covalent bonds with nylon fibers when applied simultaneously with the dyes in a dyebath. Such covalently bonded protective entities will exhibit excellent durability and longevity in spite of frequent and repeated washings or cleanings of the fibers. In addition, these protective entities, when applied simultaneously with the dyes in a dyebath, will assist in the level dye application of acid dyes and fiber reactive dyes to nylon fibers.
Additional advantages of this invention will become apparent from an examination of the ensuing description.
As used herein, the term fiber includes filaments and fibers of all lengths and diameters, and fibers that have been formed into yarns, woven into fabrics, tufted or fusion bonded into carpets or formed into nonwoven fabrics, such as needlepunch fabrics or spunbonded or meltblown webs.
As used herein, the term fiber reactive dye refers to a type of water-soluble anionic dye that is capable of forming a covalent bond with nylon or cellulose fibers.
As used herein, the term protective entity refers to a chemical entity that may be used to protect fibers, such as (but not limited to) stain-blockers, chlorine resist agents and anti-oxidants, fire retardants and flammability protectors, ultraviolet radiation absorbers and other lightfastness protectors, antimicrobial and anti-bacterial agents, gas/fume fade protectors, mildew protectors, soil resist agents and antistats.
As used herein, the term modified protective entity refers to a protective entity that has been modified according to the invention so as to render it capable of forming a covalent bond with nylon.
The invention provides a variety of protective entities which will react to form covalent bonds with nylon and which can be applied directly in the dyebath with the dyes that are used to dye the nylon without blocking such dyes or interfering with their color yield. Such protective entities include stain-blockers, chlorine resist agents, fire retardants, UV absorbers, antimicrobial agents, fume fade protectors, soil-resist agents and anti-stats. According to this method, a protective entity is reacted with a moiety having the capability of forming a covalent bond with a nylon fiber to create a modified protective entity that is adapted to form a covalent bond with a nylon fiber. The modified protective entity is added to a dyebath containing one or more dyes selected from the group consisting of fiber reactive dyes, acid dyes, acid-premetalized dyes and disperse dyes. The dyebath is applied to nylon fiber at a pH within the range of about 0.5 to about 6.5, and an alkali solution is then applied to the fiber.
In order -to facilitate an understanding of the invention, a detailed description of the presently preferred embodiments of the invention is provided herein. It is not intended, however, that the invention be limited to the particular embodiments described or to use in connection with the dyeing procedures described herein. Various modifications and alternative embodiments such as would ordinarily occur to one skilled in the art to which the invention relates are also contemplated and included within the scope of the invention described and claimed herein.